fix error where mvn hangs if anything is output to stderr

Author: Paul Marbach

.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+  "java.configuration.updateBuildConfiguration": "automatic"
+}

shared/src/main/kotlin/org/javacs/kt/classpath/MavenClassPathResolver.kt

@@ -5,6 +5,7 @@ import org.javacs.kt.util.findCommandOnPath
 import java.nio.file.Path
 import java.nio.file.Files
 import java.io.File
+import java.io.InputStream
 
 /** Resolver for reading maven dependencies */
 internal class MavenClassPathResolver private constructor(private val pom: Path) : ClassPathResolver {
@@ -58,21 +59,34 @@ private fun mavenJarName(a: Artifact, source: Boolean) =
     if (source) "${a.artifact}-${a.version}-sources.jar"
     else "${a.artifact}-${a.version}.jar"
 
-private fun generateMavenDependencyList(pom: Path): Path {
-    val mavenOutput = Files.createTempFile("deps", ".txt")
-    val workingDirectory = pom.toAbsolutePath().parent.toFile()
-    val cmd = "$mvnCommand dependency:list -DincludeScope=test -DoutputFile=$mavenOutput"
-    LOG.info("Run {} in {}", cmd, workingDirectory)
-    val process = Runtime.getRuntime().exec(cmd, null, workingDirectory)
-
-    process.inputStream.bufferedReader().use { reader ->
+private fun readInputStream(process: Process, inputStream: InputStream) {
+    inputStream.bufferedReader().use { reader ->
         while (process.isAlive) {
             val line = reader.readLine()?.trim() ?: break
             if (line.isNotEmpty() && !line.startsWith("Progress")) {
                 LOG.info("Maven: {}", line)
             }
         }
     }
+}
+
+private fun generateMavenDependencyList(pom: Path): Path {
+    val mavenOutput = Files.createTempFile("deps", ".txt")
+    val workingDirectory = pom.toAbsolutePath().parent.toFile()
+    val cmd = "$mvnCommand dependency:list -DincludeScope=test -DoutputFile=$mavenOutput"
+    LOG.info("Run {} in {}", cmd, workingDirectory)
+    val process = Runtime.getRuntime().exec(cmd, null, workingDirectory)
+
+    val inputStream = Thread() { readInputStream(process, process.inputStream) }
+    val errorStream = Thread() { readInputStream(process, process.errorStream) }
+
+    // start the streams in parallel...
+    inputStream.start()
+    errorStream.start()
+
+    // ...then block on both of them
+    inputStream.join()
+    errorStream.join()
 
     return mavenOutput
 }